Understand one thing - you will wipe your pump out. There is no way to flush the debris effectively out of the pump. It has to be disassembled. You want to power flush the system? Locate the return hose. Fab up a hose extension for it on place it in a container. Start the engine and add oil to oil tank as needed. Keep the level up high to avoid possible aeration The clean oil will go through the system and empty into the container. Wheels shold be up and turning. Do it as long as you see fit. WHAT DO YOU OWN??????? 2-3 qt system (older Toro/Exmark) should require 2 gallons to flush. I've done this to change nasty old neglected oil, but never to clean a system, because it's not very effective. Good luck